The present invention relates to a method and apparatus for manufacturing article stoppers known also as tag pins, for attaching such as labels or tags to merchandise or connecting together a plurality of articles.
With the stopper devices to which the present invention most broadly relates and which are generically represented by letter T in the accompanying drawings, those today most widely utilized have individually a generally H-shaped overall structure as shown in FIGS. 1 and 2 of the accompanying drawings, which individually comprise a head portion 1, a crossbar member 2 and a filament portion 3 connecting between the same, which are integrally formed by molding a synthetic resin capable of undergoing molecular orientation, such as nylon and so forth.
The stoppers having the above structure are required to have the filament portion stretched as thin as possible so as not to seriously impair the article through which the stopper is applied and yet rigid enough to permit the crossbar member to restore its original condition as soon as it has been applied through an article by an attacher device.
For satisfying the above requirements, the sectional area of the filament portion 3 is reduced by stretching, and end part of the filament at which the filament is connected to the crossbar or lateral rod member is especially made fine but tough and flexible by molecular orientation. The fact that the filament portion is tough and flexible means that when it is pierced through an article, the lateral rod or crossbar 2 can immediately restore its original condition (in a T-letter relation to the filament portion). Accordingly, whether the filament portion 3 is appropriately stretched or not assumes an extreme importance in having the quality of the stopper device determined.
As apparatus for stretching the article stopper device T, there can be mentioned an apparatus which utilizes molds per se and also an apparatus in which a blank stopper is once taken out of the mold and is then stretched. Apparatus of the former type is proposed and disclosed in, for example, Japanese Patent Publication No. 46-37100. In this known apparatus, the mold for manufacturing the stopper device is arranged so that the head portion and the lateral rod are moved relative to each other in the lengthwise directions of the filament. More specifically, a blank of the stopper product is formed, and one or both of the mold parts by which the head portion and crossbar are formed respectively are moved in the direction or directions apart from each other while the blank stopper is received in the mold, to thereby have the filament portion stretched a predetermined length. In other words, in this known technique both the molding of the blank of a product stopper and stretching of the filament portion are performed by utilizing the same molds, and this known method is advantageous in that it can provide a molded article having a fine structure and that a high productivity is obtainable because it can perform the stretching operation without the need of once taking the stopper blank out of molds.
In the mold for use in practising the known method under consideration, portions are formed where the lateral rod or crossbar and the head portion confront each other (called "butting portion") and while the head portion and the crossbar are hung on these butting portions of the mold, both the crossbar and the head portion are moved relatively so that they are separated from each other, whereby the filament portion is stretched.
Whereas in the Patent Publication above referred to specific movements of mold members are recited with reference to illustrations in FIGS. 6 to 9, according to the disclosure in the Publication a pin for parting the crossbar member and the head portion from each other should necessarily be built in the cavity of the mold and when the molded stopper product is parted from the mold, both the end faces of the stopper with respect to the widthwise direction should be pressed by this pin.
As well known in the art, sizes of now commercially available stopper devices are very small, and in general, the diameter of the crossbar is about 0.7 to about 1.0 mm and the thickness of the head portion is about 0.6 to about 1.0 mm. In order to withdraw such fine crossbar or lateral rod or head portion from the mold, a put-out or push-out pin should have a size equal to or smaller than the above-mentioned size of the crossbar or head portion.
Accordingly, the structure of the mold is complicated and the put-out pin or the like is readily worn or damaged. Further, a space should be formed between the mold and the put-out pin for operating this put-out pin. However, if there is a space exceeding 2/100 mm between the mold and the pin, a flash is formed about the crossbar or lateral rod, or the head portion, and if this space is larger than 5/100 mm, a considerably large flash is formed. The presence of such flash is not allowed at all in the stopper device because an article to which the device is attached, especially a garment or the like, is readily damaged by catching of the device on fibers or the like. Namely, this defect is conspicuous in case of fibrous articles, garments and the like. Moreover, this put-out or push-out pin, that is reciprocated in the mold at a high speed at every cycle of molding, involves various problems. For example, the pin is sintered while the molding operation is repeated and peeling is caused between the pin and the mold. Further, the pin per se is bent or in an extreme case, the pin is broken.
Through experience it has been found that a synthetic resin readily adheres to the mold just after molding and the molded synthetic resin is hardly pushed out or put out by the use of a put-out or push-out pin such as mentioned above just after molding. Namely, in many cases, the put-out pin is intruded into the head portion or the lateral rod or crossbar to damage a molded product. Furthermore, when such put-out pin is used repeatedly, the put-out end thereof is roughened and in this state, the crossbar or head portion of the stopper device to be put out adheres to the roughened end of the pin and the parting property of the molded product is reduced. Therefore, when all the spare pins are exchanged, the mold per se should be replaced by a new one.
FIG. 3 is a perspective view, illustrating the state where a projecting flash 4 is formed on the side end of head portion 1. In this case, the outer periphery of the head portion 1 comes to have an irregular configuration and the commercial value of the stopper device is degraded. The flash is not highly damaging because it does not catch on a garment or the like. However, if there is formed a clearance or space in the joint portion between mold parts, a petal-like flash 5 as shown in FIG. 4 is projected from the head portion 1. Such thin petal-like flash 5 readily catches on a garment or the like and tends to damage an article. Therefore, article stoppers having a flash of this kind are usually discarded as defective products.
FIG. 5 illustrates a product stopper device having projected petal-like flash 6 corresponding to a combination of flashes shown in FIGS. 3 and 4. The flash 6 of this type is characterized in that the portion corresponding to the petal is relatively small in size.
When a resin is injected into the cavity of a mold under a high pressure, the high pressure is naturally imposed on the article being molded and it is permitted to undergo expansion. Accordingly, even if it is intended to put out the molded article by means of a pin, the molded article tightly adheres to the cavity of the mold and it cannot be shifted with ease. Moreover, the molded article is still in the softened state. Accordingly, if it is intended to put out the molded article forcibly, the projecting pin is caused to sink into the head portion and dent 7 is formed as shown in FIG. 6.
The force for withdrawing the molded article from the mold corresponds to the sum of the force of adherence of the molded article to the mold, the pressing force of the molded article expanded by the molding pressure to the wall of the cavity of the mold, and the like. In order to resist this force, the put-out pin should have a size of at least 1 mm. If the put-out pin is made thick, there is brought about a problem that the thickness of the head portion is proportionally increased. The head portion occupies the majority of the synthetic resin constituting the stopper device. Accordingly, reduction of the quantity of the synthetic resin occupied by the head portion is significant from an economical viewpoint and is important for reducing the size of the mold (in many cases, it becomes unnecessary to inject the resin under a high pressure). However, in the conventional apparatus for production of article stopper device, since a put-out pin as mentioned before should inevitably be used, reduction of the thickness is limited by provision of the put-out pin and it is impossible to decrease the thickness of the head portion.